ADMINISTRATION AND ABSORPTION

The route of administration, the absorption and the distribution, together with the metabolism and the excretion of a drug, can profoundly affect its use in man. There are four general routes by which a drug may be administered

(i) orally, or less-commonly rectally, via the gastrointestinal tract;

(ii) through the skin by topical (local) application;

(iii) by injection (parenterally), which may be either intravenous or intramuscular; and

(iv) by inhalation. Each route has its particular advantages dependent on the condition that is being treated.